Warships have been sprouting more and more antennae for all the various communication equipment on board — more every year, as new devices are rolled out of development and into active service. This creates problems, especially with smaller vessels, as the multiple antennae need to be spaced far enough apart to avoid mutual interference with signals. The US Navy may have come up with a liquid solution:
With an $80 water pump, a $15 rubber hose and a $20 electrical device called a current probe that was easily plugged into a hand-held radio, [Daniel Tam] produced a spout roughly four metres tall from the waters of San Diego Bay. With this he could send and receive a clear signal. Over the intervening years his invention, dubbed the “pee antenna” by incredulous colleagues, has been tweaked and improved to the point where it can transmit over a distance of more than 50km (30 miles).
To make a seawater antenna, the current probe (an electrical coil roughly the size and shape of a large doughnut) is attached to a radio’s antenna jack. When salt water is squirted through the hole in the middle of the probe, signals are transferred to the water stream by electromagnetic induction. The aerial can be adjusted to the frequency of those signals by lengthening or shortening the spout. To fashion antennae for short-wave radio, for example, spouts between 18 and 24 metres high are about right. To increase bandwidth, and thus transmit more data, such as a video, all you need do is thicken the spout. And the system is economical. The probe consumes less electricity than three incandescent desk lamps.
A warship’s metal antennae, which often weigh more than 3½ tonnes apiece, can be damaged in storms or combat. Seawater antennae, whose components weigh next to nothing and are easily stowable, could provide handy backups — and, eventually, more than backups. Not all of a ship’s antennae are used at once, so the spouts could be adjusted continuously to obtain the types needed at a given moment. According to SPAWAR, ten such antennae could replace 80 copper ones.
